How much fluid is "one drop"?

[Jim Reynolds]

I seem to remember from high school chemistry some official definition
of how many milliliters of fluid are contained in one drop. I don't
have any texts handy which give this definition. Am I crazy or does
this definition really exist? And is it going to be pretty reliable,
i.e., no matter which eyedropper I use, will my drops be about that
amount as long as I hold the dropper vertical? Exactly how many
mililiters *is* it?

Thanks in advance,

Jim Reynolds

[Don Wiles]

Jim Reynolds (j...@marlin.ssnet.com) wrote:

: I seem to remember from high school chemistry some official definition

: Thanks in advance,

: Jim Reynolds
There can be no formal definition, since the size of a drop will
depend on several things--mostly the surface tension of the liquid. A
rule of thumb that is roughly good for aqueous solutions is that 20
drops will be about 1 mL.

[Tony DeVito]

Don Wiles (dwi...@superior.carleton.ca) wrote:
: Jim Reynolds (j...@marlin.ssnet.com) wrote:

: : I seem to remember from high school chemistry some official definition
: : of how many milliliters of fluid are contained in one drop. I don't

: : Jim Reynolds
<cut stuff>
: There can be no formal definition, since the size of a drop will

: depend on several things--mostly the surface tension of the liquid. A
: rule of thumb that is roughly good for aqueous solutions is that 20
: drops will be about 1 mL.

I agree for water about 1/20 ml
When I spent more time in the field I used to make up my own test kits
and I used to (please don't laugh) calibrate the droppers I used for
titrations. I almost always got 15 to 25 drops per ml the difference
being the specific solution (surface tension, density) and the shape and
size of the orifice on the dropper.

Just count out 100 drops and see if that gives you 5 ml. Toss the
droppers that have an unacceptable varience.

Try not to think about losing count at 85 ;-}

regards,
to...@dorsai.dorsai.org

[Gillian Gardner]

When using a Pasteur pipette, it takes about 40 drops to get 1 mL. Just thought I'd add my 2 cents worth.

[The Erlenmeyer Flask]

>Thanks in advance,

I believe that the definition of "one drop" is 0.05 mL. So, 20 drops
makes up 1 mL.

--
------Earl W. Reed, General Manager - WRUR-640 AM/88.5 FM Rochester, NY------
"The Erlenmeyer Flask" Go Bills!!!!!!!!!
University of Rochester Go Sabres!!!!!!!!
er0...@uhura.cc.rochester.edu Go Orangemen!!!!!

[st...@chem.queensu.ca]

Why don't you just use a graduated cylinder and see how many drops it takes
to make a certain volume and then find the ratio.

[Ernest S. Tomlinson]

From long, painful, and now entirely useless experience using burettes--

A drop is 0.05 mL--20 to the milliliter. This was amazingly consistent.
Drops from Pasteur pipettes tended to be about 0.05 mL, I seem to remember
as well--maybe a bit less.

-et (titrations, anyone?)
--
Ernest Tomlinson e-mail at e...@ugcs.caltech.edu; phone calls and mail ignored.
"I don't much approve of _The Hobbit_ myself, preferring my own mythology...to
this rabble of Eddaic-named dwarves out of Voluspa, newfangled hobbits and
gollums (invented in an idle hour), and Anglo-Saxon runes." - J. R. R. Tolkien

[Jim Reynolds]

In article <CxwHt...@cunews.carleton.ca>,

Don Wiles <dwi...@superior.carleton.ca> wrote:
>Jim Reynolds (j...@marlin.ssnet.com) wrote:
>
>: I seem to remember from high school chemistry some official definition
>: of how many milliliters of fluid are contained in one drop. I don't
>: have any texts handy which give this definition. Am I crazy or does
>: this definition really exist? And is it going to be pretty reliable,
>: i.e., no matter which eyedropper I use, will my drops be about that
>: amount as long as I hold the dropper vertical? Exactly how many
>: mililiters *is* it?
>

>There can be no formal definition, since the size of a drop will
>depend on several things--mostly the surface tension of the liquid. A
>rule of thumb that is roughly good for aqueous solutions is that 20
>drops will be about 1 mL.

I tried measuring it this morning. It took 2300 drops to fill 50 mL,
so that's 21-22 microliters per drop. The liquid is a hydraulic
fluid.

I also found someone else who'd tried to do something similar to what
I'm doing, and he got 33 microliters to the drop. Interesting that
there is such a difference, though he was using a different brand of
fluid than what I'm using; I don't know if the composition is similar.

Thanks to all of you for your responses.

Jim

--
Who is General Failure, and why is he reading my disk?

[yod...@wittenberg.edu]

A "drop" is a highly imprecise way to measure fluid volume or mass. As others
have stated in answer to this question, this quantity varies greatly depending
on factors such as:
(1) SURFACE TENSION OF THE LIQUID
(2) GEOMETRY AND DIAMETER OF THE DISPENSING APPARATUS
(3) DENSITY OF THE FLUID
(4) VISCOSITY OF THE FLUID

and so on. You are better off using a scale or pipet/volumetric dispensing
device if you are trying to measure quantity of a material.
Mark P. Smith
BSChEexit

[Michael K. Richmann]

Exactly, I can't say. But, one drop is about 0.01 ml (this from my
eluent prep procedures using a 100-1000 microliter pipet).

Mike

[Peter Lundberg]

I would say that a drop (aqueous solution) is about 30 ul.

O==O ================================== O==O
O==O Peter Lundberg O==O
O==O Email: pet...@umdix.umdc.umu.se O==O
O==O ============761.91141============= O==O

[UZS...@ibm.rhrz.uni-bonn.de]

In article <38193s$b...@marlin.ssnet.com>

hi Jim !
It depends on the liquid you work with. For water which is dropped from
a pipette one drop is 0.05 ml.
martin